CN110267748B - Cooling device for hot-rolled steel sheet and cooling method for hot-rolled steel sheet - Google Patents

Abstract

The purpose is to improve the uniformity of temperature in the rolling direction and the width direction of the hot-rolled steel sheet by appropriately cooling the lower surface of the hot-rolled steel sheet after finishing rolling in the hot-rolling step, and a cooling method of the hot-rolled steel sheet A device for cooling the lower surface of a hot-rolled steel sheet conveyed on a conveying roller after finishing rolling in a hot rolling process, characterized in that the cooling device includes a width-divided cooling belt that conveys the lower surface of the steel sheet conveying region The cooling area delimited by the entire area in the plate width direction and the predetermined length in the rolling direction is used as the total cooling area, and the total cooling area is divided into a plurality of areas in the plate width direction. It is a cooling area obtained by dividing the width-split cooling strip into a plurality of areas in the rolling direction; at least one cooling water nozzle sprays cooling water to each lower surface of the divided cooling surface; The cooling water sprayed from the nozzle switches between collision and non-collision with the divided cooling surface; a width direction thermometer that measures the temperature distribution in the width direction of the plate; and a control device that controls the operation of the switching device based on the measurement result of the width direction thermometer .

Description

Cooling device for hot-rolled steel sheet and cooling method for hot-rolled steel sheet

Technical Field

The present invention relates to a cooling device for cooling the lower surface of a hot-rolled steel sheet conveyed by a conveyor roll after finish rolling in a hot rolling process, and a cooling method using the cooling device.

Background

With the recent weight reduction of automobiles, the demand for high-tensile steel sheets among hot-rolled steel sheets has increased, and the quality required of hot-rolled steel sheets has further improved. In particular, in recent years, not only high strength but also excellent workability such as press formability and hole expandability, and variation in mechanical properties such as tensile strength and workability are required to be controlled within a predetermined range over the entire area of the steel sheet.

However, during cooling after finish rolling, there are cases where uneven temperature distribution occurs in the sheet width direction of the hot-rolled steel sheet for various reasons. As a specific example, a stripe-like uneven temperature distribution that extends in the rolling direction of the hot-rolled steel sheet in the sheet width direction can be given. There are several reasons, including those due to the finish rolling before cooling after the finish rolling and the scale remaining in the descaling process performed before the finish rolling, those due to the distribution of the lubricant material remaining scattered at the time of the finish rolling in the sheet width direction, those due to the unevenness of the cooling water injection portion provided between the rolling mills of the finish rolling mill, and those due to the heating furnace. Even if the finish rolling is followed by cooling, uneven temperature distribution or the like may occur due to maintenance failure of the cooling device.

In addition, in the manufacturing process of the hot-rolled steel sheet, one of the factors that greatly affect the properties of the final product as described above is the coiling temperature. Therefore, in order to improve the quality of the steel sheet, it is important to improve the uniformity of the coiling temperature over the entire area of the steel sheet. Here, the coiling temperature refers to the temperature of the steel sheet immediately before the coiling apparatus when the steel sheet is coiled after the cooling step after the finish rolling.

In general, in a cooling step of spraying cooling water to a high-temperature steel sheet of 800 to 900 ℃ after finish rolling, vapor generated by film boiling stably covers the surface of the steel sheet while the temperature of the steel sheet is about 600 ℃ or higher. Therefore, the cooling capacity of the cooling water itself is reduced, but it becomes easier to uniformly cool the steel sheet over the entire surface.

However, particularly from the steel sheet temperature of less than about 550 ℃, the steel sheet temperature decreases and the amount of generated steam decreases. Further, the vapor film covering the surface of the steel sheet starts to break down, and becomes a transitional boiling region in which the distribution of the vapor film changes temporally and spatially. As a result, the unevenness of cooling increases, and the unevenness of the temperature distribution in the width direction and the rolling direction of the steel sheet tends to rapidly increase. Therefore, it is difficult to control the temperature of the steel sheet, and it is difficult to complete cooling of the entire steel sheet at the desired coiling temperature.

On the other hand, in order to produce a product having excellent properties in terms of both strength and workability, it is effective to reduce the winding temperature to a low temperature range of 500 ℃. Therefore, it is very important to control the unevenness of the coiling temperature across the entire steel sheet, including the distribution in the width direction and the longitudinal direction, within a predetermined range with respect to the target temperature. From such a viewpoint, a large number of inventions for controlling the coiling temperature have been made so far.

Many of these inventions relate to a method and means for preventing uneven cooling caused by the cooling device itself. In particular, in hot-rolled steel sheets, uneven cooling in the sheet width direction, which is caused by the cooling water sprayed onto the upper surface side of the steel sheet remaining on the steel sheet, is a great problem, and various measures have been taken. In addition, many inventions have been found to solve the above problems, including uneven temperature distribution in the width direction and the longitudinal direction of the steel sheet before cooling, and reduction of uneven cooling due to unevenness in surface properties such as roughness and scale thickness of the steel sheet surface, which are caused by factors other than the cooling apparatus. That is, particularly in the case where the coiling temperature is in the low temperature region, the vapor film is first broken in the low temperature portion due to the uneven temperature distribution before cooling, and enters the transition boiling region to be rapidly cooled, and therefore, there is a problem that the temperature deviation after cooling is enlarged as compared with the temperature deviation on the inlet side of the cooling device. Further, the influence of the surface unevenness also causes a problem that the vapor film is selectively broken first at a portion having a large surface roughness or a portion having a thick oxide scale, and the temperature deviation after cooling is enlarged several times as large as that of the inlet side of the cooling device.

As a countermeasure against uneven cooling caused by the inconsistency between the temperature and the surface property before the cooling, it is most desirable to implement some means so that the inconsistency becomes sufficiently small before the cooling. In fact, a number of inventions relating to such countermeasures have also been made. However, in a large-scale manufacturing facility such as a manufacturing line of a hot-rolled steel sheet, productivity and cost are also important. Even if there is a measure for improving the unevenness of the temperature and the surface property before cooling, it is actually very difficult to completely implement the unevenness improving measure before cooling until the problem after cooling is completely eliminated in the process of balancing the overall cost. Further, the causes of the unevenness of the surface properties are many in the portions which have not been elucidated in terms of mechanism, and there are cases where no fundamental measures have been found.

Therefore, as another means for coping with the unevenness before cooling, there is considered a means of: the amount of cooling is selectively limited for low-temperature portions or increased for high-temperature portions based on the temperature distribution information before or during cooling, thereby making the temperature distribution uniform after cooling. It is also considered that the temperature distribution after cooling can be made uniform as follows. That is, the inconsistency in the surface properties such as the scale is not necessarily grasped from the temperature distribution information before cooling. However, the influence thereof tends to occur in the temperature distribution during cooling. Thus, consider the following: the temperature distribution is measured at an appropriate timing, that is, at a timing before the vapor film is damaged and a fatal uneven temperature distribution is generated, and the temperature distribution is measured, and the amount of cooling is controlled based on the information, whereby the temperature distribution after cooling can be uniformized.

Therefore, the following inventions have been made so far.

For example, patent document 1 discloses a method of cooling a steel plate by using a spray range control device in which a spray header in which spray nozzles having on-off valves opened/closed according to a pilot pressure are arranged is provided with a control cylinder for supplying a pilot pressure for opening/closing the on-off valves of the respective spray nozzles, and the internal pressure in the control cylinder is controlled by the position of a piston rod moving on a screw rotated by a variable motor, thereby controlling the discharge of cooling water from the spray nozzles, wherein an edge mask, or a front mask and a rear mask are formed by adjusting an operating pilot pressure applied to the on-off valves of specific preset spray nozzles among a plurality of spray nozzles provided in the spray header.

Patent document 2 discloses a cooling device for a steel pipe, including: a spraying device which sprays fluid to the cooling water sprayed toward the steel pipe to change the flow of the cooling water to a direction not contacting with the steel pipe; and a tub receiving the cooling water whose flow direction is changed by the spray device.

Patent document 3 discloses a cooling apparatus for a hot-rolled material, the cooling apparatus including: a circular tube-shaped header having a slit for ejecting a plate-shaped water flow; and a width adjustment body which is formed with a concave part gradually blocking the water flow from the width direction end part of the sprayed water flow to the width direction center and can rotate concentrically with the header.

Patent document 4 discloses that: in the cooling apparatus, a plurality of nozzles for adding coolant to the hot-rolled steel sheet are provided in the width direction on both sides of the upper and lower surfaces of the hot-rolled steel sheet, and these nozzles are controlled in such a manner that coolant is added to a position where a particularly high temperature can be detected. In this cooling device, a plurality of temperature sensors are further provided along the width direction, and these temperature sensors detect the temperature distribution in the width direction of the hot-rolled steel sheet, and are configured to be able to control the amount of coolant from the nozzle based on the signals of the temperature sensors and in dependence on the signals.

Patent document 5 discloses that: in the cooling apparatus, a plurality of cooling water headers in which a plurality of cooling water supply nozzle groups are arranged linearly are arranged above the hot-rolled steel sheet in the width direction, and the flow rate of the cooling water is controlled based on a temperature distribution measured by a temperature distribution sensor that detects a temperature distribution in the sheet width direction. Specifically, on-off control valves are provided in these cooling water headers, and the cooling water is controlled by the on-off control valves.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 7-314028

Patent document 2: japanese Kokai publication Sho 58-81010

Patent document 3: japanese examined patent publication No. 62-25049

Patent document 4: japanese Kohyo publication No. 2010-527797

Patent document 5: japanese laid-open patent publication No. 6-71328

Disclosure of Invention

Problems to be solved by the invention

Regarding the hot rolled steel sheet, the steel sheet is conveyed at a very high speed (≈ take-up speed) up to several meters/second to twenty meters/second. Therefore, in order to switch between starting and stopping the cooling water spray from the cooling water spray nozzles based on the uneven temperature distribution in the rolling direction of the steel sheet before and during the cooling, it is necessary to shorten the response time of the switching as much as possible and to perform the control at a high speed.

In order to eliminate uneven temperature distribution in the sheet width direction of the steel sheet before and during cooling, it is necessary to switch between starting and stopping the spraying of cooling water from the cooling water nozzles arranged along the sheet width direction, at high speed, for each cooling water nozzle or for each of a plurality of cooling water nozzles. However, the response time of the cooling device used in the cooling process of the conventional hot-rolled steel sheet is about 1 to 3 seconds. Therefore, the hot rolled steel sheet is also conveyed by ten meters to several tens meters during the response time. Therefore, particularly in the case of an uneven temperature distribution of a steel sheet that varies at a pitch of about 10 m or less in the rolling direction, it is not possible to sufficiently suppress the uneven temperature distribution after cooling from expanding.

In the technique disclosed in patent document 1, nozzles incorporating an on-off valve that opens and closes in response to a pilot pressure are arranged in the plate width direction. Further, the range of the pilot pressure required for closing the cooling water injection can be selected within a range set in advance in the plate width direction, and the injection of the cooling water can be selectively stopped. This makes it possible to control the cooling water injection on/off in accordance with the low-temperature portions at the edge and front and rear ends of the steel sheet.

However, the response time of on/off of the cooling water injection depends on the moving speed of the piston rod. In the technique disclosed in patent document 1, since the movement is performed in accordance with the rotation of the screw, the amount of movement is small, and it is difficult to perform on/off control about 3 times or more for 1 second. Therefore, there is a limit to coping with uneven temperature distribution at a fine pitch (for example, 10 m or less).

Further, the technique disclosed in patent document 2 discloses that the state in which cooling is not performed is achieved by changing the flow direction of the cooling water for cooling the steel pipe, but only by this switching technique, temperature control cannot be performed at any position in the plate width direction of the steel plate.

In the technique disclosed in patent document 3, the baffle plate is rotated so that the cooling water flow does not contact the end portion of the steel plate, but temperature control cannot be performed at any position in the plate width direction of the steel plate.

In addition, in the cooling device described in patent document 4, it is disclosed to control the amount of the coolant from the nozzle in the plate width direction, but it is not specifically disclosed how to control the amount of the coolant. That is, fig. 8 of patent document 4 shows a case where nozzles are arranged in a line in the plate width direction, but it is not disclosed how to control the coolant on the upstream side of the pipe connected to the nozzles. For example, in the case where the pipe connected to the nozzle is not filled with the coolant, if the coolant amount is simply controlled, the responsiveness when the coolant is added from the nozzle is poor. Since the steel sheet is transported at a very high speed of several meters/second to twenty several meters/second, in order to control the amount of cooling water colliding with the steel sheet by switching between the start of spraying cooling water from a part of the cooling water nozzles and the stop of spraying cooling water based on the uneven temperature distribution in the longitudinal direction of the steel sheet before and during the cooling, it is necessary to shorten as much as possible the time required for switching from the state of spraying cooling water to the stop of spraying and from the state of stopping spraying cooling water to the start of spraying, that is, the response time, and to enable high-speed control.

Further, patent document 4 discloses control of the amount of coolant in the plate width direction, but does not disclose control of the coolant in the rolling direction. In this case, it is difficult to suppress the uneven temperature distribution in a stripe shape extending along the rolling direction of the hot-rolled steel sheet. Further, since water is present on the upper surface, the temperature of the hot-rolled steel sheet in the width direction cannot be sufficiently controlled. In view of the above, the cooling device described in patent document 4 does not achieve sufficient homogenization of the temperature of the hot-rolled steel sheet in the sheet width direction, and thus there is room for improvement.

The cooling device described in patent document 5 has the same problem as that of patent document 4 described above. That is, the cooling water is controlled by the on-off control valve, and the responsiveness is still poor in a state where, for example, the pipe connected to the nozzle is not always filled with the cooling water as described above. Further, although a plurality of cooling water headers are provided in the sheet width direction, it is difficult to suppress the uneven temperature distribution in the form of stripes because only one cooling water header is provided in the rolling direction, and the temperature control in the rolling direction of the hot-rolled steel sheet is impossible.

In addition, in the cooling device of patent document 5, cooling is performed by spraying cooling water onto the upper surface of the hot-rolled steel sheet, but since water exists on the upper surface, the temperature of the hot-rolled steel sheet in the sheet width direction cannot be sufficiently controlled. Further, if the water on the plate is not properly removed, the temperature cannot be accurately measured by the temperature distribution sensor, and there is room for improvement in temperature control.

In view of the above, in the conventional cooling apparatus and cooling method, it is difficult to uniformize the temperature of the hot-rolled steel sheet in the rolling direction and the sheet width direction.

In addition, the material properties of the high-tensile steel sheet are greatly affected by cooling. Since the coiling temperature of the high-tension steel sheet has a greater influence on the characteristics of the final product than the conventional material, the strength of the high-tension steel sheet is greatly influenced by the temperature distribution that is not uniform to an extent that is not noticeable in the conventional material. Therefore, in the production of high-tensile steel sheets, cooling control with higher accuracy than in the production of conventional materials is required. The techniques proposed so far for controlling the cooling temperature of the steel sheet by using the cooling water supplied from the upper surface side of the steel sheet have the following problems, for example.

(1) The cooling water supplied from the upper surface side of the steel sheet collides with the upper surface of the steel sheet, and then remains on the upper surface of the steel sheet, thereby becoming sheet water. When the cooling water is supplied from the upper surface side, particularly in a temperature region where the temperature of the steel sheet is lower than 550 ℃, the steel sheet is cooled by on-sheet water in addition to the portion where the cooling water collides. In the high-tensile steel sheet, the influence is particularly large, and therefore the uneven temperature distribution becomes large as compared with the conventional material.

(2) The cooling water supplied from the upper surface side of the steel sheet collides with the upper surface of the steel sheet, and a part of the cooling water flows in the sheet width direction of the steel sheet. The water flowing in the width direction interferes with the cooling water supplied from the upper surface side of the steel sheet. Therefore, it is difficult to control the temperature of the steel sheet in the sheet width direction with high accuracy by the cooling water supplied from the upper surface side.

(3) In order to perform accurate cooling temperature control using cooling water supplied from the upper surface side of the steel sheet, it is necessary to remove the water on the sheet using a water removal device. In order to facilitate the improvement of the temperature measurement accuracy, the thermometer is installed at a position which is not easily affected by the water removal equipment, that is, at a position which is separated from the cooling water nozzle for spraying the cooling water in the rolling direction. As a result, the time from the measured temperature to the collision of water becomes long, and the temperature change in this time becomes large, so that the control accuracy of the cooling temperature is lowered.

As described above, in the conventional technique of controlling the cooling temperature of the steel sheet in the sheet width direction by the cooling water supplied from the upper surface side of the steel sheet, it is difficult to perform highly accurate temperature control in the sheet width direction at a level required in the production of a high tensile steel sheet.

The present invention has been made in view of the above problems, and an object of the present invention is to improve temperature uniformity in the rolling direction and the sheet width direction of a hot-rolled steel sheet by appropriately cooling the lower surface of the hot-rolled steel sheet after the finish rolling in the hot rolling step.

Means for solving the problems

The invention according to claim 1 provides a cooling device for a hot-rolled steel sheet for cooling a lower surface of the hot-rolled steel sheet conveyed by a conveyor roller after finish rolling in a hot rolling process, the cooling device comprising: a width-divided cooling zone in which all cooling zones defined by a predetermined length in the rolling direction and all zones in the width direction of the steel sheet on the lower surface of the steel sheet conveying zone are defined as all cooling zones, and each cooling zone is obtained by dividing the all cooling zones into a plurality of zones in the width direction of the steel sheet; a divided cooling surface which is a cooling region obtained by dividing the width-divided cooling strip into a plurality of regions in the rolling direction; at least one cooling water nozzle that sprays cooling water to each lower surface of the divided cooling surfaces; a switching device that switches between collision and non-collision of the cooling water sprayed from the cooling water nozzle with the divided cooling surface; a width direction thermometer that measures a temperature distribution in a board width direction; and a control device for controlling the operation of the switching device based on the measurement result of the width direction thermometer.

Here, "collision with the divided cooling surfaces" in "collision and non-collision of the cooling water sprayed from the cooling water spray nozzle with the divided cooling surfaces" refers to spraying of the cooling water such that the cooling water collides with the lower surface of the hot-rolled steel sheet when the lower surface of the hot-rolled steel sheet is present on the divided cooling surfaces. On the other hand, the phrase "not collide with the divided cooling surfaces" means a state in which the cooling water does not collide with the lower surface of the hot-rolled steel sheet when the lower surface of the hot-rolled steel sheet is present on the divided cooling surfaces.

In the cooling device for a hot-rolled steel sheet according to claim 1, one or more cooling water nozzles may be provided for each divided cooling surface.

In the hot-rolled steel sheet according to claim 1, the number of cooling water nozzles may be different from each other in the rolling direction between the adjacent divided cooling surfaces of the cooling device.

In the cooling device for a hot-rolled steel sheet according to claim 1, the length in the rolling direction of each of the divided cooling surfaces included in the width-divided cooling zone may be different from each other in the rolling direction.

In the cooling device for a hot-rolled steel sheet according to claim 1, the length of the divided cooling surfaces in the rolling direction may be a multiple of the length between the feed rolls.

In the cooling device for a hot-rolled steel sheet according to claim 1, the arrangement of the plurality of cooling water nozzles in the sheet width direction may be arranged as follows: the distances between the centers of the cooling water nozzles adjacent in the sheet width direction are all equal.

In the cooling device for a hot-rolled steel sheet according to claim 1, a plurality of cooling water nozzles for cooling the same divided cooling surface are arranged, and the switching device can collectively and simultaneously control a switching control system for switching between collision and non-collision of the cooling water of the plurality of cooling water nozzles with respect to the same divided cooling surface.

In the cooling device for a hot-rolled steel sheet according to claim 1, the switching device may include: a water supply header pipe which is provided in a pipe through which cooling water supplied to the cooling water nozzle flows and which supplies the cooling water; a drain header or drain area that drains the cooling water; and a valve that switches the flow of cooling water between the water supply header and the water discharge header or the water discharge area.

In this case, the valve may be a three-way valve, or the three-way valve may be provided on the lateral side of the conveying roller in the plate width direction and disposed at the same height as the tip of the cooling water nozzle.

In the cooling device for a hot-rolled steel sheet according to claim 1, the switching device may include: a water supply header pipe which is provided in a pipe through which cooling water supplied to the cooling water nozzle flows and which supplies the cooling water; a drain region that drains the cooling water; a component for changing the spraying direction of the cooling water sprayed from the cooling water nozzle; and a member for blocking the cooling water from colliding with the divided cooling surfaces when the spray direction is changed, wherein the collision or non-collision of the cooling water with the lower surfaces of the divided cooling surfaces can be switched by the member for changing the spray direction of the cooling water.

In the cooling device for a hot-rolled steel sheet according to claim 1 described above, the width-direction thermometer may be provided on at least one of the rolling-direction upstream side and the rolling-direction downstream side of the entire cooling zone, and may be provided for each of the width-divided cooling zones. In this case, the width direction thermometer may be disposed on the lower surface side of the steel sheet conveying area.

The invention according to claim 2 provides a method for cooling a hot-rolled steel sheet, comprising cooling a lower surface of the hot-rolled steel sheet conveyed by a conveyor after finish rolling in a hot rolling step, wherein the entire cooling zone of the lower surface of the steel sheet conveying zone defined by the entire region in the sheet width direction and a predetermined length in the rolling direction is defined as an entire cooling zone, each cooling zone obtained by dividing the entire cooling zone into a plurality of regions in the sheet width direction is defined as a width-divided cooling zone, each cooling zone obtained by dividing the width-divided cooling zone into a plurality of regions in the rolling direction is defined as a divided cooling surface, the temperature distribution of the hot-rolled steel sheet in the sheet width direction is measured, and based on the measurement result of the temperature distribution, for each divided cooling surface, the collision and non-collision of the cooling water with the hot rolled steel sheet by the cooling water nozzles is controlled in each of the width direction and the rolling direction.

In the above-described means 2, a plurality of cooling water nozzles for spraying cooling water may be provided on the same divided cooling surface, and the collision and non-collision of the cooling water sprayed from the plurality of cooling water nozzles with the hot-rolled steel sheet existing on the same divided cooling surface may be simultaneously controlled for the plurality of cooling water nozzles in a unified manner.

In the above-described claim 2, the method may further include: a water supply header pipe which is provided in a pipe through which cooling water supplied to the cooling water nozzle flows and which supplies the cooling water; a drain header or drain area that drains the cooling water; and a valve that switches the flow of cooling water between the water supply header and the water discharge header or the drain region, controls the opening and closing of the valve based on the measurement result of the temperature distribution in the sheet width direction of the hot-rolled steel sheet, and controls the collision and non-collision of the cooling water with the cooling water nozzle with the hot-rolled steel sheet in each of the sheet width direction and the rolling direction for each divided cooling surface.

Here, the valve is a three-way valve for supplying the cooling water supplied from the water supply header to an intermediate header provided with the cooling water nozzles, and the opening degree of the three-way valve may be controlled so that the cooling water from the cooling water nozzles continues to be discharged to such an extent that the cooling water does not collide with the lower surface of the hot-rolled steel sheet from the intermediate header in which the lower surface of the hot-rolled steel sheet is not cooled by the cooling water from the cooling water nozzles, or the opening degree of the three-way valve may be controlled so that the cooling water from the cooling water nozzles collides with the lower surface of the hot-rolled steel sheet from the intermediate header in which the lower surface of the hot-rolled steel sheet is cooled by the cooling water from the cooling water.

Effects of the invention

According to the present invention, the lower surface of the hot-rolled steel sheet is appropriately cooled after the finish rolling in the hot rolling step, whereby the uniformity of temperature in the rolling direction and the sheet width direction of the hot-rolled steel sheet can be improved.

Drawings

Fig. 1 is an explanatory view schematically showing the structure of a hot rolling facility 10.

Fig. 2 is a schematic perspective view showing the structure of the lower width direction control cooling device 17 according to embodiment 1.

Fig. 3 is a schematic side view showing the structure of the lower width direction control cooling device 17 according to embodiment 1.

Fig. 4 is a schematic plan view showing the structure of the lower width direction control cooling device 17 according to embodiment 1.

Fig. 5 is a diagram illustrating a divided cooling surface a3 according to an example.

Fig. 6 is an explanatory diagram focusing on the width-divided cooling zone a 2.

Fig. 7 is a diagram illustrating a divided cooling surface a3 according to another example.

Fig. 8 is a diagram illustrating a divided cooling surface a3 according to another example.

Fig. 9 is a diagram illustrating the arrangement of the divided cooling surface a3, the cooling water nozzle 20, and the temperature measuring devices 30 and 31 in the lower width direction control cooling device 17 according to embodiment 1.

Fig. 10 shows an example of the arrangement of the divided cooling surface a3 and the cooling water nozzle 20.

Fig. 11 shows an example of the arrangement of the divided cooling surface a3 and the cooling water nozzle 20.

Fig. 12 shows an example of the arrangement of the divided cooling surface a3 and the cooling water nozzle 20.

Fig. 13 shows an example of the arrangement of the divided cooling surface a3 and the cooling water nozzle 20.

Fig. 14 is a diagram illustrating an example of the mode of the temperature measuring device 30.

Fig. 15 is a diagram illustrating an example of the manner of cooling water nozzle 20.

Fig. 16 is a diagram illustrating the structure of the lower width direction control cooling device 17 in an example in which the intermediate header 21 is not provided.

Fig. 17 is a diagram illustrating the structure of the cooling water traveling direction changing device 126.

Fig. 18 is another diagram illustrating the structure of the cooling water traveling direction changing device 126.

Fig. 19 is a diagram illustrating the structure of the cooling water traveling direction changing device 226.

Fig. 20 is another diagram illustrating the structure of the cooling water traveling direction changing device 226.

Fig. 21 is a diagram illustrating the structure of the cooling water traveling direction changing device 326.

Fig. 22 is another diagram illustrating the structure of the cooling water traveling direction changing device 326.

Fig. 23 is a diagram showing a part of the temperature distribution of the upper surface of the steel sheet in the case of comparative example 1.

Fig. 24 is a view showing a part of the temperature distribution of the upper surface of the steel sheet in example 1.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. In the present specification and the drawings, the same reference numerals are given to the constituent elements having substantially the same functional configuration, and redundant description is omitted.

[ means 1 ]

Fig. 1 is an explanatory view schematically showing the structure of a hot-rolled steel sheet manufacturing apparatus (hereinafter referred to as "hot rolling facility") 10 including the cooling apparatus according to embodiment 1.

In the hot rolling facility 10, the heated slab 1 is continuously rolled with rollers interposed therebetween, and is reduced to a minimum thickness of about 1 mm to produce a hot-rolled steel sheet 2, and the hot-rolled steel sheet 2 is wound up. The hot rolling facility 10 includes a heating furnace 11 for heating the slab 1, a width direction rolling mill 12 for rolling the slab 1 heated in the heating furnace 11 in a width direction, a roughing mill 13 for rolling the slab 1 rolled in the width direction from the top and bottom to form a rough slab, a finishing mill 14 for further continuously finish-rolling the rough slab to a predetermined thickness, cooling devices 15, 16, 17 for cooling the hot-rolled steel sheet 2 finish-rolled by the finishing mill 14 with cooling water, and a winding device 19 for winding the hot-rolled steel sheet 2 cooled by the cooling devices 15, 16, 17 into a roll shape. Of the cooling devices 15, 16, and 17, the upper cooling device 15 is disposed above the steel sheet conveying area, and the lower cooling device 16 and the lower width direction control cooling device 17 are disposed below the steel sheet conveying area.

The heating furnace 11 performs a process of heating the slab 1, which is inputted from the outside through the charging port, to a predetermined temperature. After the heat treatment in the heating furnace 11 is completed, the slab 1 is transported out of the heating furnace 11, passes through the width direction rolling mill 12, and then shifts to a rolling process by the roughing mill 13.

The supplied slab 1 is rolled by the roughing mill 13 into a rough slab (thin slab) having a thickness of about 30 to 60 mm, and is supplied to the finishing mill 14.

The fed rough slab is rolled to a thickness of about several millimeters by the finishing mill 14 to obtain the hot-rolled steel sheet 2. The hot-rolled steel sheet 2 obtained by rolling is conveyed by conveying rolls 18 (see fig. 2 to 4), and is sent to the upper cooling device 15, the lower cooling device 16, and the lower width direction control cooling device 17.

The hot-rolled steel sheet 2 is cooled by the upper cooling device 15, the lower cooling device 16, and the lower width direction control cooling device 17, and wound into a roll shape by the winding device 19.

The structure of the upper cooling device 15 is not particularly limited, and a known cooling device can be applied. For example, the upper cooling device 15 includes a plurality of cooling water nozzles that spray cooling water vertically downward from above the steel sheet conveying area toward the upper surface of the steel sheet conveying area. As the cooling water nozzle, for example, a slit laminar flow nozzle, a tube laminar flow nozzle, or the like can be used. From the viewpoint of ensuring the cooling capacity, it is preferable to provide the upper cooling device 15, and if the cooling is not insufficient, the upper cooling device is not necessarily arranged, but is usually required.

The lower cooling device 16 is a cooling device as follows: the configuration of the cooling device is not particularly limited, and a known cooling device can be applied to the cooling device, in which cooling water is sprayed vertically upward from below the steel sheet conveyance area conveyed by the conveying rollers 18 of the run-out table toward the lower surface of the steel sheet conveyance area to cool the steel sheet conveyance area.

Next, the structure of the lower width direction control cooling device 17 will be explained. Fig. 2 is a perspective view schematically showing a part of the structure of the lower width direction control cooling device 17, fig. 3 is a side view schematically showing a part of the structure of the lower width direction control cooling device 17, as viewed from the plate width direction (Y direction), and fig. 4 is a plan view schematically showing a part of the structure of the lower width direction control cooling device 17, as viewed from above in the vertical direction (Z direction).

The lower width direction control cooling device 17 in the present embodiment is roughly configured to include a cooling water nozzle 20, a switching device including an intermediate header 21, a pipe 23, a water supply header 25, a three-way valve 24, and a drain header 26, temperature measuring devices 30 and 31, and a control device 27.

The lower width direction control cooling device 17 is a device for controlling cooling of a divided cooling surface A3 that is formed by dividing the entire cooling area a1, which is the lower surface of the steel sheet conveying area, described later. Fig. 5 to 8 show diagrams for explanation thereof. Fig. 5 to 8 are diagrams illustrating the divided cooling surface a 3. Fig. 5 to 8 are views of the hot rolling mill 10 viewed from the Z direction, and show the relationship between the total cooling area a1 described later and the positions of the feed rolls 18. In fig. 5 to 8, the conveying roller 18 is shown by a broken line for convenience of explanation.

In the present embodiment, a region where the hot-rolled steel sheet 2 that can be manufactured by the hot rolling facility 10 can exist when being conveyed on the run-out table is referred to as a "steel sheet conveying region". The "steel sheet conveying region" is a three-dimensional region extending in the rolling direction and divided by the maximum sheet thickness × the maximum sheet width of the hot-rolled steel sheet that can be produced. Therefore, the "steel plate conveying area" occupies an area on the run-out table from the outlet side end of the finishing mill to before the coiler in the rolling direction.

Of the lower surface of the "steel plate conveying area", the area to be cooled by the lower width direction controlled cooling device 17 and defined by the entire area in the plate width direction and a predetermined length in the rolling direction are referred to as "entire cooling area a 1".

The "entire region in the sheet width direction" indicates a region where the hot-rolled steel sheet 2 can exist on the transport rollers 18. The "predetermined length in the rolling direction" is a length of at least two pitches or more between the rolls in the rolling direction of the feed roll 18. The "length of one pitch between the rolls in the rolling direction" refers to a distance between the axes of the conveying rolls adjacent in the rolling direction. The length of the "predetermined length in the rolling direction" is not particularly limited, but is preferably about 20 m or less from the viewpoint of facility cost. The specific length may be determined as appropriate according to the cooling capacity of the lower width direction control cooling device 17 and the predicted form of the uneven temperature distribution of the hot-rolled steel sheet 2.

Each cooling zone obtained by dividing the entire cooling zone a1 into a plurality of zones in the plate width direction is referred to as a "width-divided cooling zone a 2". Fig. 6 shows an example in which the steel sheet conveying area a1 is divided into 6 width-divided cooling zones a 2. In the example shown in fig. 6, 6 width-divided cooling zones a2 are arranged in the plate width direction in order to facilitate understanding of the technique, but the number of divisions is not limited to this. The number of the width-divided cooling zones a2 in the sheet width direction (i.e., the number of divisions) is not particularly limited, but the division into at least one cooling water nozzle 20 corresponds to each width-divided cooling zone a 2.

The widthwise length of the divided-width cooling zone a2 is a length obtained by dividing the widthwise length of the steel sheet conveying area a1 by the number of divisions. The length of the width-divided cooling zone a2 in the plate width direction is not particularly limited, and may be set to 50 mm, 100 mm, or the like as appropriate.

Each of the cooling regions obtained by dividing the width-divided cooling zone a2 into a plurality of regions in the rolling direction is referred to as a "divided cooling surface A3". The length of the divided cooling surface A3 in the sheet width direction is the same as the length of the width-divided cooling zone a2 in the sheet width direction, and the length of the divided cooling surface A3 in the rolling direction is a length obtained by dividing the length of the width-divided cooling zone a2 in the rolling direction by the number of divisions.

The length of the divided cooling surface a3 in the rolling direction is not particularly limited and can be set as appropriate. The length of the divided cooling surface a3 in the rolling direction shown in fig. 5 is set to be equal to one pitch between the rollers in the rolling direction of the feed roller 18. Fig. 7 shows an example of the length set to the amount of two pitches between the rollers in the rolling direction of the conveying roller 18. The length of the divided cooling surface a3 in the rolling direction may be any length that is an integral multiple of the pitch between the rolls of the conveying rolls 18 in the rolling direction.

The lengths of the plurality of divided cooling surfaces a3 arranged adjacent to each other in the rolling direction are not necessarily the same, and may be different from each other. For example, as shown in fig. 8, the rolling direction lengths of the divided cooling surfaces a3 may be increased in order from the upstream side to the downstream side to be set to the amounts of one pitch, two pitches, four pitches, eight pitches, sixteen pitches, and … between the rolling direction rolls of the delivery rolls 18.

In the following description, as shown in fig. 9, a divided cooling surface a3 having a rolling direction length four times the rolling direction inter-roller pitch of the conveying rollers 18 will be described as an example. In the present embodiment, as shown in fig. 9, the divided cooling surfaces a3 having a rolling direction length four times the rolling direction inter-roller pitch of the conveying rollers 18 are provided. However, as described above, other forms of the divided cooling surface a3 may be applied.

The cooling water nozzles 20 are cooling water nozzles that spray cooling water vertically upward from below the steel sheet conveying area of the run-out table toward the lower surface of the steel sheet conveying area, and a plurality of cooling water nozzles 20 are arranged. Various known types of nozzles can be used for the cooling water nozzle 20, and for example, a pipe laminar flow nozzle can be cited. The cooling range of the cooling water nozzle 20 in the plate width direction is set to be equal to or less than the length of the cooling split surface A3 in the plate width direction so that the collision range of the cooling water with the cooling split surface A3 does not enter the other cooling split surface A3.

Fig. 9 also shows the arrangement of the cooling water nozzle 20 with respect to the divided cooling surface a3 in the present embodiment. The cooling water nozzle 20 is denoted by "●" in fig. 9. At least one cooling water nozzle 20 is disposed toward each of the divided cooling surfaces a 3.

In this embodiment, the four cooling water nozzles 20 are arranged so that the four cooling water nozzles 20 belong to one divided cooling surface a3 in a plan view of the steel sheet conveying area as viewed from above. In this embodiment, four cooling water nozzles 20 are arranged between the adjacent feed rolls 18 in plan view and aligned in the rolling direction. The number and arrangement of the cooling water nozzles 20 belonging to one divided cooling surface a3 are not particularly limited, and may be one or a plurality of. The number and arrangement of the cooling water nozzles 20 may also be different between the adjacent divided cooling surfaces a 3.

The amount of water and the flow rate of water discharged from the cooling water nozzles 20 are the same for each cooling water nozzle 20 in the sheet width direction and the rolling direction, and the cooling capacity can be easily controlled to be the same. Further, the number, the water discharge amount, and the water discharge flow rate of the cooling water nozzles 20 provided to the respective cooling split surfaces A3 aligned in the sheet width direction at the same position in the rolling direction are made the same, and the control is facilitated so that the cooling capacity of the respective split cooling surfaces A3 aligned in the sheet width direction is made the same.

In addition, in the cooling water nozzles 20 belonging to the divided cooling surfaces a3 arranged in the sheet width direction, the ejection water flow rate and the ejection flow rate are the same, it is preferable that the arrangement is such that the distances between the centers of the cooling water nozzles 20 adjacent in the sheet width direction are all equal. This enables uniform cooling in the plate width direction with higher accuracy.

In addition, even if the cooling capacity based on the discharge water amount and the discharge flow rate of the cooling water nozzles 20 are different in the sheet width direction and the rolling direction, the control can be performed by the control device 27.

In this embodiment, two of the divided cooling surfaces a3 are arranged in the rolling direction (X direction), and six are arranged in the plate width direction (Y direction). The cooling water nozzles 20 having the same discharge water amount and discharge flow rate are also arranged in the rolling direction and the sheet width direction.

Fig. 9 shows the arrangement of the divided cooling surface A3 and the cooling water nozzles 20 belonging to the divided cooling surface A3 in the present embodiment, but the present invention is not limited thereto, and various combinations can be applied. Fig. 10 to 13 exemplify the above. Here, the amount/flow rate of the discharged water is the same for each cooling water nozzle, and the cooling capacity is set to be the same.

In the example shown in fig. 10, the length of the divided cooling surfaces A3 in the rolling direction is equal to the distance between the rolls of the feed rolls 18 in the rolling direction, and one cooling water nozzle 20 belongs to each divided cooling surface A3.

In the example shown in fig. 11, the length of the divided cooling surfaces A3 in the rolling direction is set to one pitch between the rolls of the feed rolls 18 in the rolling direction, and two cooling water nozzles 20 are arranged on each divided cooling surface A3. The two cooling water nozzles 20 may be arranged in the rolling direction or in the sheet width direction. Further, as shown in fig. 11, the rolling direction and the plate width direction may be shifted from each other.

In the example shown in fig. 12, the length of the divided cooling surfaces A3 in the rolling direction is equal to the distance between the rolls of the feed rolls 18 in the rolling direction, and four cooling water nozzles 20 are arranged on each divided cooling surface A3.

The example shown in fig. 13 is an example of: the rolling direction length of the divided cooling surfaces A3 changes from the upstream side to the amount of one pitch, the amount of two pitches, the amount of four pitches, and the amount of eight pitches … between the rolling direction rolls of the delivery rolls 18, and the number of cooling water nozzles 20 belonging to each divided cooling surface A3 differs among the divided cooling surfaces A3 adjacent in the rolling direction.

The intermediate header 21 functions as a part of the switching device in the present embodiment, and is a header that supplies cooling water to the cooling water nozzles 20. In this embodiment, as can be seen from fig. 2 to 4, the intermediate header 21 is a tubular member extending in the rolling direction, and a plurality of cooling water nozzles 20 are provided in the rolling direction. Thus, it is possible to simultaneously control the injection of the cooling water from the cooling water nozzles 20 arranged in one intermediate header 21 and the stop of the injection of the cooling water. In the illustrated example, four cooling water nozzles 20 are arranged in the rolling direction with respect to one intermediate header 21, but the number of cooling water nozzles 20 is not limited to this.

The intermediate header 21 is disposed in a one-to-one correspondence with one of the divided cooling surfaces a 3. This makes it possible to perform switching control between the injection and the stop of the injection of the cooling water for each of the divided cooling surfaces a 3.

In this embodiment, since the divided cooling surfaces A3 are provided in two in the rolling direction, there are only two intermediate headers 21 in the rolling direction, but the number of the intermediate headers 21 may be appropriately changed depending on the number of the divided cooling surfaces A3.

The three-way valve 24 is a member that functions as a part of the switching device in the present embodiment. That is, the three-way valve 24 is a main component of a switching device that switches between collision and non-collision of the cooling water sprayed from the cooling water nozzles 20 with the lower surface of the steel sheet conveying area.

The three-way valve 24 of the present embodiment is a valve of a split type, which switches between guiding water from the water supply header 25 to the pipe 23, supplying the water to the intermediate header 21, and further supplying the water to the cooling water nozzle 20, and guiding the water to the drain header 26. In this embodiment, the drain header 26 is exemplified as a drain portion, but the form thereof is not particularly limited.

Instead of the three-way valve 24 of the present embodiment, two check valves (broadly, valves for checking the flow of fluid, which may be referred to as on/off valves) may be provided, and the control may be performed in the same manner as the three-way valve.

In this embodiment, the three-way valve 24 is provided with one intermediate header 21 and is disposed between a water supply header 25 for supplying cooling water and a water discharge header 26 for discharging the cooling water. However, the present invention is not limited to this, and one three-way valve 24 may be disposed in each of the plurality of intermediate headers 21. This enables the plurality of intermediate headers 21 to be simultaneously controlled in a unified manner.

In the illustrated example, two water supply headers 25 and two water discharge headers 26 are provided, but the number of the water supply headers 25 and the number of the water discharge headers 26 are not limited to this, and may be, for example, one.

The inside of the pipe 23 is always filled with cooling water by the three-way valve 24. Thus, when the cooling water is caused to collide with the lower surface (divided cooling surface a3) of the steel sheet conveying area, that is, when the lower surface of the hot-rolled steel sheet 2 is cooled, the time from the instruction to open the three-way valve 24 to the injection of the cooling water from the cooling water nozzles 20 can be shortened, and the responsiveness can be improved. The responsiveness of opening and closing the three-way valve 24 is preferably 0.5 seconds or less. The three-way valve 24 may use, for example, a solenoid valve.

Further, the three-way valve 24 is preferably disposed at the same height as the front end of the cooling water nozzle 20. More specifically, it is preferable that the connection point of the three-way valve 24 to the pipe 23 is at the same height as the tip of the cooling water nozzle 20. Thus, the tip of the cooling water nozzle 20 and the tip of the pipe 23 are at the same height, and the inside of the pipe 23 is always filled with cooling water. Even if the three-way valve 24 is not sealed completely and the coolant leaks to a large extent, the interior of the pipe 23 can be filled with the coolant, and the responsiveness can be further improved.

Preferably, the three-way valve 24 is provided on the lateral side in the sheet width direction with respect to the conveyance roller 18. It is also conceivable to provide the three-way valve 24 below the conveyance roller 18, for example, but the space below the conveyance roller 18 is limited, and it is difficult to provide a plurality of three-way valves 24. Further, it is also difficult to perform maintenance of the three-way valve 24 below the conveying roller 18. In this regard, if the three-way valve 24 is provided on the lateral side in the plate width direction with respect to the conveying roller 18 as in this embodiment, the three-way valve 24 can be provided with a high degree of freedom, and maintenance can be easily performed.

The upstream temperature measuring device 30 is disposed at a position on the lower surface side of the steel sheet conveying area, functions as a width direction thermometer, and measures the temperature of the hot-rolled steel sheet 2 on the upstream side in the rolling direction of the entire cooling area a 1.

Preferably, the upstream temperature measuring devices 30 are disposed so as to correspond to the respective width-divided cooling zones a2, and therefore, in the illustrated example, six upstream temperature measuring devices 30 are provided so as to be aligned in the plate width direction and to be able to measure the temperature on the upstream side of the respective width-divided cooling zones a2 (i.e., the temperature before cooling). Thereby, the temperature of the hot-rolled steel sheet 2 on the upstream side of the lower widthwise control cooling device 17 in the sheet width direction can be measured over the entire width.

The downstream temperature measuring device 31 is disposed at a position on the lower surface side of the steel sheet conveying area, functions as a width direction thermometer, and measures the temperature of the hot-rolled steel sheet 2 on the downstream side in the rolling direction of the entire cooling area a 1.

Preferably, the downstream temperature measuring devices 31 are disposed so as to correspond to the width-divided cooling zones a2, and in the illustrated example, six downstream temperature measuring devices 31 are arranged in the plate width direction so as to be able to measure the temperature of each of the cooled width-divided cooling zones a 2. This makes it possible to measure the temperature of the hot-rolled steel sheet 2 downstream of the lower width-direction control cooling device 17 in the rolling direction in the width direction over the entire width.

The control device 27 is a device that controls the operation of the switching device based on either one of the measurement result of the upstream temperature measuring device 30, the measurement result of the downstream temperature measuring device 31, or both. Therefore, the control device 27 includes an electronic circuit or a computer that performs calculation based on a predetermined program, and the upstream temperature measuring device 30, the downstream temperature measuring device 31, and the switching device are electrically connected to the control device 27.

Specifically, the temperature of the hot-rolled steel sheet 2 conveyed on the run-out table after the finish rolling is measured by the upstream temperature measuring device 30. The measurement result is transmitted to the control device 27, and the cooling amount necessary for uniformizing the temperature of the hot-rolled steel sheet 2 is calculated for each divided cooling surface a 3.

Further, based on the calculation result, the control device 27 feedforward-controls the opening and closing of the three-way valve 24. That is, the controller 27 controls the opening and closing of the three-way valve 24 so as to realize the cooling amount for uniformizing the temperature of the hot-rolled steel sheet 2 for each of the divided cooling surfaces A3, and controls the collision and non-collision of the cooling water injected from the cooling water nozzles 20 with the lower surface of the hot-rolled steel sheet 2 for each of the divided cooling surfaces A3.

Further, since the divided cooling surfaces a3 are arranged in the width direction and the rolling direction, respectively, the control device 27 can control the temperature in both the width direction and the rolling direction, and can make the temperature of the hot-rolled steel sheet 2 uniform with high accuracy.

In addition, the feedforward control is useful in order to suppress the stripe-like uneven temperature distribution extending in the rolling direction of the hot-rolled steel sheet 2, and from this viewpoint, the temperature in the sheet width direction of the hot-rolled steel sheet 2 can be further uniformized by the feedforward control using the upstream side temperature measuring device 30.

However, the opening and closing of the three-way valve 24 may be feedback-controlled based on the measurement result of the downstream temperature measuring device 31, without being limited to the feedforward control. That is, the measurement result of the downstream temperature measuring device 31 is used to perform calculation by the control device 27, and the number of open/close operations of the three-way valve 24 is controlled for each cooling split surface a3 based on the calculation result. Thereby, collision and non-collision of the cooling water with the lower surface of the steel sheet conveying area can be controlled for each of the divided cooling surfaces a 3.

In the lower width direction control cooling device 17, it is possible to selectively perform feed-forward control of the three-way valve 24 based on the measurement result of the upstream side temperature measuring device 30 and feedback control of the three-way valve 24 based on the measurement result of the downstream side temperature measuring device 31.

Further, the feedback control may be applied as correction control of the feedforward control result. In this way, in the lower lateral direction control cooling device 17, the feedforward control of the three-way valve 24 based on the measurement result of the upstream side temperature measuring device 30 and the feedback control of the three-way valve 24 based on the measurement result of the downstream side temperature measuring device 31 can be performed in a unified manner.

In the case where only one of the feedforward control and the feedback control is performed, either one of the upstream temperature measuring device 30 and the downstream temperature measuring device 31 may be omitted.

In the lower lateral direction control cooling device 17, the three-way valve 24 is provided in the intermediate header 21, and the three-way valve 24 is disposed at the same height as the tip of the cooling water nozzle 20, so that the inside of the pipe 23 can be filled with the cooling water at all times. Therefore, when the cooling water injected from the cooling water nozzle 20 is controlled by controlling the opening and closing of the three-way valve 24 based on the temperature measurement results of the upstream side temperature measurement device 30 and/or the downstream side temperature measurement device 31, the responsiveness thereof can be made excellent.

In order to fill the interior of the pipe 23 with the cooling water more reliably, the cooling water may be continuously discharged from the cooling water nozzle 20 at all times. That is, the opening degree of the three-way valve 24 is controlled so that the cooling water from the cooling water nozzles 20 continues to be discharged to such an extent that the cooling water does not collide with the divided cooling surfaces A3, with respect to the intermediate header 21 where the cooling water from the cooling water nozzles 20 does not collide with the divided cooling surfaces A3. On the other hand, the opening degree of the three-way valve 24 is controlled so that the cooling water from the cooling water nozzles 20 collides with the divided cooling surfaces A3 with respect to the intermediate header 21 where the cooling water from the cooling water nozzles 20 collides with the divided cooling surfaces A3. In this case, since the interior of the pipe 23 is reliably filled with the cooling water, the responsiveness can be ensured.

In the lower width direction control cooling device 17 of the above-described embodiment, the configurations of the upstream side temperature measuring device 30 and the downstream side temperature measuring device 31 are not particularly limited as long as they are configured to measure the temperature of the hot-rolled steel sheet 2, but for example, a temperature measuring device described in japanese patent No. 3818501 or the like is preferably used. Fig. 14 is a schematic explanatory view showing the structure of the upstream temperature measuring device 30.

The upstream temperature measuring device 30 includes a radiation thermometer 32 for measuring the temperature of the hot-rolled steel sheet 2, an optical fiber 33 having a tip arranged at a position facing the steel sheet conveying area (hot-rolled steel sheet 2) and a rear end connected to the radiation thermometer 32, a nozzle 34 as a water column forming part for jetting water toward the lower surface of the steel sheet conveying area so as to form a water column between the steel sheet conveying area and the tip of the optical fiber 33, and a water reservoir 35 for supplying water to the nozzle 34. The upstream side temperature measuring device 30 receives the radiation light from the lower surface (hot-rolled steel sheet 2) of the steel sheet conveying area through the water column by the radiation thermometer 32, thereby measuring the lower surface temperature of the hot-rolled steel sheet 2.

Here, since cooling water from the cooling water nozzle 20 and the like are generally present on the lower surface of the steel sheet conveying area, when a general thermometer is used, a measurement error due to the cooling water occurs. Therefore, in order to provide a thermometer, it is necessary to remove the cooling water and obtain a section (for example, several meters) in which the cooling water does not exist in the rolling direction.

In contrast, in the upstream temperature measuring device 30, since the radiation thermometer 32 receives the radiation light via the water column from the nozzle 34, the influence of the cooling water can be suppressed by the water column, and the measurement error caused by the cooling water can be reduced. Therefore, the upstream temperature measuring device 30 can be brought close to the cooling water nozzle 20 on the most upstream side without providing a section where no cooling water is present. Therefore, the responsiveness can be further improved. In order to ensure sufficient responsiveness, the distance between the upstream-side temperature measuring device 30 and the most upstream-side cooling water nozzle 20 is preferably within 5 meters, and more preferably within 1 meter.

Further, since the hot-rolled steel sheet 2 makes a meandering motion on the run-out table, if the distance between the upstream side temperature measuring device 30 and the cooling water nozzle 20 on the most upstream side is long, there is a possibility that the temperature measuring position and the cooling position in the sheet width direction of the hot-rolled steel sheet 2 are different. In this case, in particular, the vicinity of the widthwise end of the hot-rolled steel sheet 2 may not be cooled.

In contrast, in this embodiment, since the upstream side temperature measuring device 30 can be brought close to the cooling water nozzle 20 on the most upstream side, the temperature measuring position and the cooling position in the sheet width direction of the hot-rolled steel sheet 2 can be reliably aligned, and the hot-rolled steel sheet 2 can be appropriately cooled.

The configuration of the downstream temperature measuring device 31 is also the same as that of the upstream temperature measuring device 30, and the same effects as those of the upstream temperature measuring device 30 described above can be obtained.

The intermediate header 21 is provided with a three-way valve 24, and the controllability of the cooling water to be sprayed to the hot-rolled steel sheet 2 is improved so that the number of cooling water nozzles 20 in the intermediate header 21 is small. On the other hand, if the number of cooling water nozzles 20 is reduced, the number of three-way valves 24 required increases accordingly, and the facility cost and the running cost increase. Therefore, the number of cooling water nozzles 20 can be set in consideration of these balances.

When the cooling water is caused to collide with the divided cooling surfaces A3, the rolling direction length of the entire cooling zone a1 becomes longer when a small amount of cooling water is used. Therefore, it is preferable to spray, for example, 1m from the cooling water nozzle 20³/m²Cooling water with large water volume and density above min.

In the lower width direction control cooling device 17, as shown in fig. 15, a plurality of spray holes 40 for spraying cooling water may be provided at the tip of the cooling water nozzle 20. The plurality of injection holes 40 are provided at equal intervals on a projection surface in the plate width direction (Y direction). For example, when a large flow rate of cooling water is injected from a single injection hole of the cooling water nozzle 20, the cooling water collides with one portion in the sheet width direction of the hot-rolled steel sheet 2, and therefore, a stripe-like uneven temperature distribution is likely to occur. In contrast, by providing a plurality of injection holes 40, the collision pressure of the cooling water against the divided cooling surface a3 can be reduced. Therefore, the uneven temperature distribution in the form of a stripe can be more reliably suppressed, and the temperature of the hot-rolled steel sheet 2 in the sheet width direction can be further uniformized.

In the above embodiment, the intermediate header 21 is provided, but the present invention is not limited to this embodiment, and a system without the intermediate header 21 may be employed. Fig. 16 is a schematic plan view showing the structure of the lower width direction control cooling device 17 of this embodiment. Fig. 16 corresponds to fig. 4, and a three-way valve 24 is connected to each cooling water nozzle 20, but for ease of understanding, the three-way valve 24, the water supply header 25, and the water discharge header 26 are not shown in fig. 16.

In the embodiment shown in fig. 16, a pipe, not shown, is connected to each cooling water nozzle 20, and a three-way valve is provided in the pipe. The three-way valve is provided between a water supply header for supplying cooling water and a water discharge header for discharging the cooling water in a pipe. Even in such a mode in which one three-way valve is provided for one cooling water nozzle 20, the same effects as those obtained in the above-described mode can be obtained. In this case, the idea of dividing the cooling surface a3 is also the same as that of the lower width direction control cooling device 17 shown in fig. 4.

The lower width direction control cooling device 17 in the example shown in fig. 1 is disposed upstream of the lower cooling device 16, but the location of the lower width direction control cooling device 17 is not limited to this example.

If the lower width direction control cooling device 17 is disposed upstream of the lower cooling device 16 as in the example shown in fig. 1, the uneven temperature distribution generated in the hot-rolled steel sheet 2 can be removed at the initial stage of the cooling process.

On the other hand, if the lower width direction control cooling device 17 is disposed in the middle of the lower cooling device 16, even if the cooling by the upper cooling device 15 and the lower cooling device 16 is uneven, the uneven temperature distribution caused by this can be removed.

Further, by providing the lower width direction control cooling device 17 on the downstream side of the lower cooling device 16, the uneven temperature distribution of the winding temperature can be reduced.

Since the effect of the arrangement of the lower width direction control cooling device 17 with respect to the lower cooling device 16 is different in this way, the arrangement location may be determined appropriately from the viewpoint of the type of steel to be produced and the facility cost. In addition, from the viewpoint of suppressing the uneven temperature distribution as much as possible, it is preferable to dispose the lower cooling device 16 upstream, in the middle, and downstream, respectively.

[ means 2 ]

In the 2 nd aspect, in the lower width direction control cooling device 117 disposed in place of the lower width direction control cooling device 17 of the hot rolling mill 10, the cooling water traveling direction changing devices 126, 226, 326 and the guide plate 125 are disposed in place of the three-way valve 24 of the switching device of the 1 st aspect, and although there is a drain area, there is no drain header. Since the same structure as that of embodiment 1 can be applied to the other structures, the same reference numerals as those in embodiment 1 are given thereto, and descriptions thereof are omitted.

Fig. 17 and 18 are diagrams illustrating an example of a switching device including a cooling water traveling direction changing device 126 in the switching device according to the 2 nd embodiment, and are diagrams showing focusing on the periphery of one cooling water nozzle 20 disposed between the conveying rollers 18.

In this example, the switching means includes the guide plate 125 and the cooling water traveling direction changing means 126.

The guide plate 125 is a plate-like member disposed between the intermediate header 21 and the divided cooling surface a 3. The guide plate 125 is designed with sufficient strength to withstand the collision of the leading end of the hot-rolled steel sheet 2 even when the hot-rolled steel sheet 2 passes. The guide plates 125 are disposed at least between the adjacent conveying rollers 18. This can prevent the leading end of the hot-rolled steel sheet 2 from catching on the cooling water nozzles 20, the intermediate header 21, and the feed rollers 18 during passage.

The guide plate 125 is provided with an injection port 125a, and the injection port 125a allows the cooling water injected from the cooling water nozzle 20 to pass therethrough without injecting the gas from the cooling water traveling direction changing device 126. Thereby, the cooling water sprayed from the cooling water nozzles 20 collides with the divided cooling surfaces a3 through the guide plate 125, and appropriate cooling can be performed. The guide plate 125 may be provided with a drain hole through which drain water passes.

The distance between the upper surface of the guide plate 125 and the divided cooling surface a3 is not particularly limited, and may be, for example, about 20 mm.

The guide plate 125 includes a sheet 125b having a jet port 125a and formed parallel to the rolling direction, and dewatering plates 125c and 125d provided to hang downward from the lower surface of the sheet 125 b. The water removal plate 125c is provided closer to the ejection port 125a than the water removal plate 125 d.

When the gas is injected from the cooling water traveling direction changing device 126, the water deflector 125c, 125d prevents the cooling water injected from the cooling water nozzle 20 from scattering toward the injection port 125a after colliding with the sheet 125 b. The water plates 125c and 125d also suppress the cooling water from flying from the injection port 125a to the steel sheet conveyance area side and colliding with the divided cooling surface a3 due to the flow of the injected gas.

In addition, the water removal plate 125d also has the following functions: when the gas is injected from the cooling water traveling direction changer 126, the water deflector 125d prevents the cooling water injected from the cooling water nozzle 20 from scattering toward the cooling water nozzle 20 side after colliding with the sheet 125b, and from interfering with the cooling water jet injected from the cooling water nozzle 20. The water eliminator 125d is provided so as not to obstruct the flow of the cooling water spray ejected from the cooling water nozzles 20 and the flow of the gas ejected from the cooling water traveling direction changer 126.

Here, if the length of the dewatering plate 125c is too long, the cooling water jets directly collide with each other, and the amount of cooling water that flies from the jet port 125a to the steel plate conveyance area side increases, and therefore the length of the dewatering plate 125c is desirably set to about 10 mm to 30 mm.

On the other hand, the length of the dewatering plate 125d is preferably about 50 mm to 150 mm as long as the length that can sufficiently prevent the above interference is ensured.

The cooling water traveling direction changing device 126 is a device that sprays gas onto the cooling water sprayed from the cooling water nozzles 20 to change the traveling direction of the cooling water. The cooling water running direction changing device 126 is configured to include a gas manifold 127, a gas branch pipe 128, a valve 129, and a gas nozzle 130.

The gas ejected from the gas nozzle 130 controls collision and non-collision of the cooling water with the divided cooling surface a3 by changing the traveling direction of the cooling water ejected from the cooling water nozzle 20.

More specifically, the gas nozzles 130 are connected to the gas manifold 127 via gas branch pipes 128, and gas (for example, air) of a predetermined pressure is supplied from the gas manifold 127. Further, a valve 129 is installed midway in the gas branch pipe 128.

The valve 129 controls the start of gas injection from the gas nozzle 130 and the stop of gas injection based on a signal from the control device 27. As such a valve, an electromagnetic valve can be cited. Further, by arranging the gas nozzles 130 in accordance with the number of cooling water nozzles 20 with respect to the cooling water nozzles 20 belonging to one divided cooling surface A3, it is possible to control the collision and non-collision of the cooling water with the lower surface of the steel sheet conveying area for each divided cooling surface A3.

As can be seen from fig. 17 and 18, the gas nozzle 130 is disposed in the vicinity of the cooling water nozzle 20. By injecting the gas from the gas nozzle 130 while inclining at an angle of about 15 degrees to 30 degrees with respect to the vertical direction, the direction of travel of the cooling water jet can be changed efficiently with a relatively small gas flow rate.

As the gas nozzle 130, a flat air nozzle that forms a fan-shaped jet flow that is relatively less likely to attenuate the collision force even when the distance from the nozzle is long is desirably used. In this case, if the diffusion angle of the fan-shaped jet flow ejected from the gas nozzle 130 is too large, the collision force is greatly attenuated when the fan-shaped jet flow collides with the cooling water jet flow, and therefore, it is desirable that the fan-shaped jet flow be adjusted so as to cover the entire width direction of the cooling water jet flow.

As shown in fig. 17, when the valve 129 is closed and no gas is injected from the gas nozzle 130, the cooling water injected from the cooling water nozzle 20 passes through the injection port 125a and collides with the divided cooling surface a3, thereby cooling the hot-rolled steel sheet 2. In fig. 17, the flow direction of the cooling water sprayed from the cooling water nozzle 20 is indicated by an arrow with a black triangle at the tip of the solid line.

On the other hand, fig. 18 is a schematic view showing a scene in which gas is ejected from the gas nozzle 130, from the same viewpoint as fig. 17. In fig. 18, the flow direction of the gas ejected from the gas nozzle 130 is indicated by an arrow with a black triangle at the tip of the broken line.

As a specific form of operating the valve 129 so as to prevent the cooling water from colliding with the divided cooling surface A3, it is possible to change the traveling direction of the cooling water jet so that the cooling water jet ejected from the cooling water nozzle 20 does not collide with the divided cooling surface A3.

The signal from the control device 27 is received through the valve 129 and operates so as to inject the gas from the gas nozzle 130 toward the cooling water jet injected from the cooling water nozzle 20. Thereby, the cooling water jet ejected from the cooling water nozzle 20 is pushed by the flow of the gas to change the direction. As a result, the cooling water collides with the lower surface of the guide plate 125, and therefore the cooling water cannot pass through the injection port 125 a. This can prevent the cooling water from colliding with the divided cooling surface a3, and stop cooling the hot-rolled steel sheet 2.

Here, the control of the switching devices by the control device 27 can be performed in the same manner as the control of the cooling device 17 in the lower width direction of the above-described 1 st embodiment.

According to this embodiment, since the cooling water, which has been prevented from colliding with the divided cooling surface A3 by the switching device, is prevented from colliding with the divided cooling surface A3, there is no need for a tub or the like for collecting the cooling water, which has been prevented from colliding with the divided cooling surface A3. Therefore, the switching device of the 2 nd aspect can be easily installed in a narrow space such as between the adjacent conveying rollers 18.

Further, the switching device of the 2 nd aspect does not perform on/off control of the cooling water injection from the cooling water nozzles 20, but controls the collision and non-collision of the cooling water jet after injection from the cooling water nozzles 20 with the hot-rolled steel sheet 2 while keeping a state in which a certain amount of cooling water is injected from the cooling water nozzles 20. Further, as means for controlling the collision and non-collision of the cooling water jet, the collision and non-collision of the cooling water with the divided cooling surface a3 are controlled by on/off control of the jet of gas from the gas nozzle 130 by the cooling water traveling direction changing device 126, instead of mechanically operating a shutter or the like.

Fig. 19 and 20 are views schematically showing a part of the lower width direction control cooling device 117 according to the modification of the 2 nd embodiment. Fig. 19 corresponds to fig. 17, and fig. 20 corresponds to fig. 18.

The lower width direction control cooling device 117 illustrated in fig. 19 and 20 is applied with a switching device using a cooling water running direction changing device 226, instead of the cooling water running direction changing device 126 of the switching device. Therefore, the cooling water running direction changing device 226 will be described here.

The cooling water traveling direction changing device 226 includes a nozzle adapter 227 and a cylinder 228. The nozzle adapter 227 is attached to the cooling water nozzle 20. Further, the nozzle adapter 227 is attached so as to be rotatable about the fixed shaft 229. The fixed shaft 229 is fixed by a support member not shown so as not to be positionally displaced. A piston rod 231 of the air cylinder 228 is connected to the nozzle adapter 227 via a rod tip shaft 230 so as to be rotatable by the rod tip shaft 230.

Therefore, the cooling water nozzle 20 can be tilted by operating the cylinder 228. That is, the cooling water can be injected upward in the vertical direction in the posture of the cooling water nozzle 20 shown in fig. 19, and by operating the cylinder 228, the cooling water nozzle 20 can be inclined at a predetermined angle with respect to the vertical direction as shown in fig. 20.

The nozzle adapters 227 are attached to the respective cooling water nozzles 20, and the cylinders 228 are attached to the respective nozzle adapters 227. The operation of the cylinder 228 can be performed by a solenoid valve, not shown. The electromagnetic valve is opened and closed by receiving a signal from the control device 27, and the direction of the cooling water nozzle 20 is controlled to be either the vertical direction or the direction inclined with respect to the vertical direction through the air cylinder 228 as described above.

As shown in fig. 19, when the cooling water nozzles 20 are controlled in the vertical direction, the cooling water jet flows through the jet ports 125a provided in the guide plates 125 and collides with the divided cooling surfaces a 3. On the other hand, as shown in fig. 20, when the cooling water nozzles 20 are controlled to be inclined with respect to the vertical direction, the direction of the cooling water jet changes by the amount of inclination of the cooling water nozzles 20, and the cooling water collides with the lower surface of the guide plate 125, and the cooling water does not collide with the divided cooling surface a 3.

In this way, by receiving a signal from the control device 27 and operating the solenoid valve, the posture of the cooling water nozzle 20 is changed, and the direction of the cooling water sprayed from the cooling water nozzle 20 is changed, so that the posture in which the cooling water is prevented from colliding with the divided cooling surface a3 and the posture in which the collision is not prevented can be switched.

Further, by connecting the intermediate header 21 and the nozzle adapter 227 by the flexible pipe (for example, a rubber pipe or the like) 232, even if the cooling water nozzle 20 is inclined as described above, the flexible pipe 232 deforms, and the displacement of the relative positions of the two can be absorbed.

The angle at which the cooling water nozzles 20 are inclined needs to be adjusted so that substantially all of the cooling water spray collides with the lower surface of the guide plate 125. On the other hand, in order to shorten the response time, it is preferable to reduce the angle at which the cooling water nozzle 20 is inclined as much as possible. From these viewpoints, it is desirable to design that substantially all of the cooling water jets collide with the lower surface of the guide plate 125 when the cooling water nozzles 20 are inclined by about 5 degrees to 10 degrees with respect to the vertical direction.

Fig. 21 and 22 are views schematically showing a part of a lower width direction control cooling device 117 according to another modification of embodiment 2. Fig. 21 corresponds to fig. 17, and fig. 22 corresponds to fig. 18.

The switching device illustrated in fig. 21 and 22 uses a cooling water running direction changing device 326 instead of the cooling water running direction changing device 126. Therefore, the cooling water traveling direction changing device 326 will be described here.

The cooling water running direction changing device 326 includes a nozzle adapter 327, a cylinder 328, and a jet flow deflector 329. Nozzle adapter 327 is mounted to cooling water nozzle 20. Further, the jet flow deflector 329 is attached to the nozzle adapter 327 so as to be rotatable about the rotation shaft 330. Further, a piston rod 332 of the air cylinder 328 is connected to the jet flow deflector 329 via a rod tip shaft 331 so as to be rotatable by the rod tip shaft 331.

Therefore, by operating the cylinder 328, the jet flow deflector 329 can be tilted. That is, in the posture of the jet flow deflector 329 shown in fig. 21, the jet flow deflector 329 is positioned so as not to contact the cooling water sprayed from the cooling water nozzles 20, and by operating the cylinder 328, the jet flow deflector 329 can be inclined at a predetermined angle with respect to the vertical direction so as to contact the cooling water sprayed from the cooling water nozzles 20, as shown in fig. 22.

The nozzle adapters 327 are attached to the respective cooling water nozzles 20, and the cylinders 328 are attached to the respective nozzle adapters 327. The operation of the cylinder 328 can be performed by a solenoid valve not shown. The electromagnetic valve is opened and closed by receiving a signal from the control device 27, and the direction of the jet flow deflector 329 is controlled to be either the vertical direction or the direction inclined with respect to the vertical direction via the cylinder 328 as described above.

As shown in fig. 21, when jet flow deflector 329 is controlled to be vertical, the cooling water jet flows through jet ports 125a provided in guide plate 125 and collides with divided cooling surface a 3. On the other hand, as shown in fig. 22, when the jet flow deflector 329 is controlled to be inclined with respect to the vertical direction, the cooling water ejected from the cooling water nozzles 20 is bent by the jet flow deflector 329, the jet direction of the cooling water jet is changed to collide with the lower surface of the guide plate 125, and the cooling water does not collide with the divided cooling surface a 3.

In this way, by the solenoid valve being operated in response to a signal from the controller 27, the posture of the jet flow deflector 329 is changed, and the direction of the cooling water sprayed from the cooling water nozzles 20 is changed, so that the posture in which the cooling water is prevented from colliding with the divided cooling surface a3 and the posture in which the collision is not prevented can be switched.

The angle at which jet flow deflection plate 329 is inclined needs to be adjusted so that substantially all of the cooling water jet collides with the lower surface of guide plate 125. On the other hand, in order to shorten the response time, it is preferable to reduce the angle of inclination of the jet flow deflector 329 as much as possible. From these viewpoints, it is desirable to design the jet flow deflector 329 to change the direction so that substantially all of the cooling water jet collides with the lower surface of the guide plate 125 when the jet flow deflector 329 is inclined by about 5 degrees to 10 degrees with respect to the vertical direction.

Thus, 3 modes have been exemplified and described as the cooling water running direction changing device. In the case where the cooling water jet is changed in direction by injecting the gas, the movable portion, the cylinder, and the like are not required. Therefore, although it is needless to say that the present invention is also applicable to a conventional method, the present invention can be easily installed in a narrow space because the device can be made smaller than the above-described method using the jet deflector and the method of inclining the cooling water nozzle. Further, the movable portion, the cylinder, and the like are not required, and thus the present invention is advantageous in terms of durability. On the other hand, although it is considered that the consumption amount of the gas (air) increases and becomes disadvantageous in terms of cost, the angle at which the direction of the cooling water jet should be changed can be made small as compared with the case where the cooling water jet is completely blocked or changed in direction to a large extent as in the conventional case, and therefore the amount of the gas (air) required is significantly reduced as compared with the conventional case, and as a result, the installation cost and the running cost of the compressor and the like are reduced.

Even in the case of using the above-described jet deflector, since the direction of the cooling water jet needs to be changed only slightly, the force applied to the jet deflector is about 10% to 20% (x sin θ times, θ: the angle of change in the direction of the cooling water jet) as compared with the case where the cooling water jet is completely shut off or changed in direction to a large extent as in the conventional case. Therefore, the impact load repeatedly received can be greatly reduced, and therefore the required strength of the movable portion of the apparatus can be reduced. This can reduce the weight of the cylinder to a large extent, reduce the thrust required for the cylinder, and reduce the cylinder diameter. Further, since the air consumption amount can be reduced, the running cost is reduced. Further, the impact load applied during the reciprocating operation of the cylinder is also reduced, and the durability can be greatly improved as compared with the conventional method.

In the above description relating to the 2 nd aspect, the following aspects are exemplified: the collision and non-collision of the cooling water jets with the divided cooling surfaces a3 are controlled by changing the direction of the cooling water jets after being jetted from the cooling water nozzles 20. However, the 2 nd aspect is not limited to this aspect, and for example, the collision or non-collision of the cooling water sprays with the split cooling surfaces may be controlled by moving the guide plates in the rolling direction, or by combining changing the direction of the cooling water sprays ejected from the cooling water nozzles and moving the guide plates in the rolling direction.

In the above description relating to the 1 st and 2 nd aspects, the following aspects are exemplified: the number of switching devices that operate to cause the cooling water to collide with the divided cooling surfaces, and the number of cooling water nozzles that spray the cooling water that collides with the divided cooling surfaces according to embodiment 2 are controlled by a control device. The present invention is not limited to this embodiment, and for example, the following embodiments are possible: in addition to controlling the number of the switching devices and the number of the cooling water nozzles, the flow rate of the cooling water sprayed from the cooling water nozzles is also controlled. The flow rate of the cooling water can be controlled using a flow rate adjusting valve. In this case, the flow regulating valve may be provided between the intermediate header and the switching device.

When the spray nozzle is used as the cooling water nozzle, the distance between the tip of the spray nozzle and the steel sheet may be changed. This makes it possible to control the collision pressure of the cooling water jet that collides with the steel sheet, and therefore, the cooling temperature can be easily controlled.

The effects of the present invention will be described below based on examples and comparative examples. The invention is not limited to this embodiment.

< example 1 >

In the verification of the effect, as the cooling device of embodiment 1, the lower width direction control cooling device 17 shown in fig. 2 was used. As the cooling device of comparative example 1, the conventional lower cooling device 16 was used without using the lower width direction control cooling device 17.

The conditions in this verification are as follows. The operating conditions of example 1 were set to the steel sheet width: 1300 mm, plate thickness: 3.2 mm, steel plate conveying speed: 600mpm, temperature before cooling: 900 ℃, target coiling temperature: at 550 ℃. The switching device of the 1 st aspect is used as the lower width direction control cooling device. However, in fig. 4, there are two intermediate headers in the rolling direction, and four cooling water nozzles are arranged in each intermediate header, but in example 1, there are four intermediate headers in the rolling direction, and two cooling water nozzles are arranged in each intermediate header. The cooling length in the rolling direction was set to eight points between the feed rolls as in fig. 4, and the response speed including the three-way valve and the piping system was 0.2 seconds. Further, the water density of the cooling water to be sprayed was set to 2m³/m²And/min. The lower width direction control cooling device is provided at a position close to the winding device (downstream side of the lower cooling device).

On the other hand, the operation conditions of comparative example 1 did not have the cooling control function in the plate width direction, and the water density of the cooling water to be sprayed was set to 0.7m³/m²/min。

Fig. 23 shows an example in which a part of the temperature distribution of the upper surface of the steel sheet in comparative example 1 is extracted. In fig. 23, in order to make the temperature distribution display easy to understand, only the distribution on the lower temperature side than the target temperature is particularly shown in a shade (the same applies to fig. 24 shown later). The light black part is a part at-30 ℃ to-15 ℃ with respect to the target temperature, and the dark part is a part at less than-30 ℃ with respect to the target temperature. As is clear from fig. 23, in comparative example 1, a relatively wide low temperature portion p is generated in the center portion in the plate width direction. Further, strip-shaped low-temperature portions q1, q2 extending in the rolling direction are also generated.

In addition, according to comparative example 1, the standard temperature deviation was 23.9 ℃. The standard temperature deviation was obtained from all the measurement points of the steel sheet temperature except for 10 meters at each of the leading and trailing ends of the steel sheet and 50 mm at each of the both ends, based on the results measured by the infrared thermography measuring device.

Fig. 24 shows an example in which a part of the temperature distribution of the upper surface of the steel sheet in example 1 is extracted. As is clear from fig. 24, in example 1, low temperature sections p, q1, and q2 were all smaller than in comparative example 1.

In addition, according to example 1, the standard temperature deviation was 8.8 ℃. Therefore, according to the present invention, it is found that the temperature of the hot-rolled steel sheet in the sheet width direction can be made uniform.

< example 2 >

The operation conditions were the same as in example 1, and the cooling length in the rolling direction of the lower width direction control cooling device was the same as in example 1, and the length was set to the length corresponding to eight points between the feed rolls. Lower width direction control cooling device in the switching device of the 2 nd aspect, the cooling water running direction changing device is the cooling water running direction changing device 126, and as shown in fig. 10, one switching device is provided on one divided cooling surface a 3. The response speed was 0.18 seconds. Further, the water density of the sprayed cooling water was set to 2m³/m²And/min. The lower width direction control cooling device is provided at a position close to the winding device (downstream side of the lower cooling device).

According to example 2, the temperature distribution of the entire surface of the steel sheet of the hot rolled steel sheet after cooling can obtain the same result as in fig. 24 with a standard temperature deviation of 8.6 ℃.

Description of the reference numerals

1. A slab; 2. hot-rolled steel sheet; 10. hot rolling equipment; 11. heating furnace; 12. a width direction rolling mill; 13. a roughing mill; 14. a finishing mill; 15. an upper side cooling device; 16. a lower side cooling device; 17. a lower width direction control cooling device; 18. a conveying roller; 19. a take-up device; 20. a cooling water nozzle; 21. an intermediate header; 23. piping; 24. a three-way valve; 25. a water supply header; 26. a drain header; 27. a control device; 30. an upstream side temperature measuring device; 31. a downstream side temperature measuring device; 32. a radiation thermometer; 33. an optical fiber; 34. a nozzle; 35. a water storage tank; 40. an injection hole; 117. a lower width direction control cooling device; 125. a guide plate; 125a, an ejection port; 125c, 125d, a dewatering plate; 126. 226, 326, a cooling water running direction changing device; 127. a gas header; 128. a gas branch pipe; 129. a valve; 130. a gas nozzle; 227. 327, a nozzle adapter; 228. 328, a cylinder; 229. a fixed shaft; 230. 331, a rod front end shaft; 231. 332, a piston rod; 232. a tube; 329. a jet deflection plate; 330. a rotating shaft.

Claims (13)

1. A cooling device for a hot-rolled steel sheet, which cools the lower surface of a hot-rolled steel sheet conveyed on a conveying roller after finish rolling in a hot rolling step, characterized in that: The cooling device includes: The width-division cooling zone is a cooling zone defined by the entire area in the sheet width direction and a predetermined length in the rolling direction on the lower surface of the steel sheet conveying area as the total cooling area, and the entire cooling area is defined in the sheet width. Each cooling area obtained by dividing it into multiple areas in the direction; A divided cooling surface, which is a cooling area obtained by dividing the width-divided cooling strip into a plurality of areas in the rolling direction; cooling water nozzles for spraying cooling water to the respective lower surfaces of the divided cooling surfaces, and one or more cooling water nozzles are arranged for each of the divided cooling surfaces; a switching device that switches between collision and non-collision of cooling water sprayed from the cooling water nozzle with the divided cooling surface; a width direction thermometer provided on at least one of an upstream side in the rolling direction and a downstream side in the rolling direction of the entire cooling region, and provided on the lower surface side of the steel sheet conveying region close to the entire cooling region, and A cooling zone divided for each of the widths is provided, and the temperature distribution in the sheet width direction of the hot-rolled steel sheet is measured; and A control device that controls the switching device for each of the divided cooling surfaces for cooling of each of the plurality of divided cooling surfaces included in the width-divided cooling zone, based on the measurement result of the width direction thermometer , so as to control the cooling over the entire length of the width-split cooling strip in the rolling direction, which is the cooling control of the entire cooling area. 2 . The cooling device for hot-rolled steel sheets according to claim 1 , wherein: 3 . The number of the cooling water nozzles arranged between the adjacent divided cooling surfaces is different from each other in the rolling direction. 3. The cooling device for hot-rolled steel sheet according to claim 1 or 2, characterized in that: The lengths in the rolling direction of the divided cooling surfaces included in the width-divided cooling strip are different from each other in the rolling direction. 4. The cooling device for hot-rolled steel sheet according to claim 1 or 2, characterized in that: The length in the rolling direction of the divided cooling surface is a multiple of the length between the conveying rolls. 5. The cooling device for hot-rolled steel sheet according to claim 1 or 2, characterized in that: The arrangement of the plurality of cooling water nozzles in the plate width direction is such that the distances between the centers of the cooling water nozzles adjacent in the plate width direction are all equal distances. 6. The cooling device for hot-rolled steel sheets according to claim 1 or 2, characterized in that: A plurality of the cooling water nozzles for cooling the same divided cooling surface are arranged, The switching device simultaneously controls a switching control system in a unified manner, and the switching control system responds to collisions and collisions between the cooling water of the plurality of cooling water nozzles with respect to the same divided cooling surface and the same divided cooling surface. Switch without collision. 7. The cooling device for a hot-rolled steel sheet according to claim 1 or 2, wherein: The switching device includes: a water supply header provided on a pipe through which cooling water supplied to the cooling water nozzle flows, and supplying cooling water; a drain header or drain area that drains the cooling water; and A valve that switches the flow of the cooling water between the water supply header and the drain header or the drain area. 8. The cooling device for hot-rolled steel sheet according to claim 7, characterized in that: The valve is a three-way valve, which is provided on the lateral side of the conveying roller in the plate width direction, and is arranged at the same height as the front end of the cooling water nozzle. 9. The cooling device for hot-rolled steel sheet according to claim 1 or 2, characterized in that: The switching device includes: a water supply header provided on a pipe through which cooling water supplied to the cooling water nozzle flows, and supplying cooling water; a drainage area, which drains the cooling water; means for changing the spray direction of the cooling water sprayed from the cooling water nozzle; and A component that blocks the cooling water from colliding with the divided cooling surface when the spray direction is changed, By means of changing the spray direction of the cooling water, it is possible to switch between collision and non-collision of the cooling water with the lower surface of the divided cooling surface. 10. A method for cooling a hot-rolled steel sheet, comprising cooling a lower surface of a hot-rolled steel sheet conveyed on a conveying roller after finish rolling in a hot rolling step, characterized in that: The cooling area delimited by the entire area in the sheet width direction and the predetermined length in the rolling direction on the lower surface of the steel sheet conveying area is taken as the total cooling area, Each cooling region obtained by dividing the entire cooling region into a plurality of regions in the plate width direction is defined as a width-divided cooling zone, The cooling area obtained by dividing the width-divided cooling strip into a plurality of areas in the rolling direction is used as a divided cooling surface, On at least one of the upstream side in the rolling direction and the downstream side in the rolling direction of the entire cooling region, on the lower surface side of the steel sheet conveying region close to the entire cooling region, and divided for each of the widths The cooling zone measures the temperature distribution in the sheet width direction of the hot rolled steel sheet, Based on the measurement result of the temperature distribution, the collision and non-collision of cooling water using cooling water nozzles with the plurality of divided cooling surfaces included in the width-divided cooling zone is controlled for each of the divided cooling surfaces, thereby controlling The cooling over the entire length of the width-divided cooling zone in the rolling direction serves as cooling control of the hot-rolled steel sheet in the entire cooling zone. 11. The cooling method of hot-rolled steel sheet according to claim 10, characterized in that, The cooling water nozzles for spraying the cooling water are provided with a plurality of the cooling water nozzles on the same divided cooling surface, and the cooling water and the presence of the cooling water using the cooling water nozzles are collectively and simultaneously controlled for the plurality of cooling water nozzles. The collision and non-collision of the hot-rolled steel sheets on the same divided cooling surface. 12. The cooling method of hot-rolled steel sheet according to claim 10 or 11, characterized in that, include: a water supply header provided on a pipe through which cooling water supplied to the cooling water nozzle flows, and supplying cooling water; a drain header or drain area that drains the cooling water; and a valve that switches the flow of the cooling water between the water supply header and the drain header or the drain area, The opening and closing of the valve is controlled based on the measurement result of the temperature distribution in the sheet width direction of the hot-rolled steel sheet, and the cooling water and the cooling water using the cooling water nozzle are controlled for each of the divided cooling surfaces. The collision and non-collision of a plurality of the divided cooling surfaces included in the width-divided cooling zone controls the cooling over the entire length of the width-divided cooling zone in the rolling direction, and becomes the source of the hot-rolled steel sheet in the entire cooling zone. Cooling control. 13. The method for cooling a hot-rolled steel sheet according to claim 12, wherein The valve is a three-way valve for supplying cooling water supplied from the water supply header to an intermediate header provided with the cooling water nozzles, The opening degree of the three-way valve is controlled for the intermediate header for which the lower surface of the hot-rolled steel sheet is not cooled by the cooling water from the cooling water nozzles so that the cooling water from the cooling water nozzles Water is continuously discharged to the extent that it does not collide with the lower surface of the hot-rolled steel sheet, With respect to the intermediate header for cooling the lower surface of the hot-rolled steel sheet with the cooling water from the cooling water nozzle, the opening degree of the three-way valve is controlled so that the cooling water from the cooling water nozzle collided with the lower surface of the hot-rolled steel sheet.

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